Generally, deposition of films has taken place in a manner such that layers are grown from the bottom in an upward direction. For example, a film grown on a wafer is often grown in a direction vertical to the wafer's surface. Other films may be grown vertically on a microstructure surface. Some examples of features created in this manner include trench filling, step formation, or FinFET features, for example.
Air gaps are features with applicability in film deposition. U.S. Pat. No. 7,304,388 to Dubin et al. discloses air gaps that are created by first forming a sacrificial interlayer dielectric and decomposing it. The formation may involve an etching step, which may cause problems and decrease the performance of the device. The formation may also involve a deposition step for protecting liners, metal or metallic surfaces, thus decreasing the size of the air gap and the performance of the device. For example, International Publication No. WO 2013/101096 to Fischer discloses air gap formation with a hood layer. The air gap formation may also include an etching step. Air gaps may be used both in back end of line (BEOL) processing or front end of line processing. Two examples of applications for air gaps include air gaps in metallization, such as Cu metallization, or air gaps in NAND memories.
As a result, a method for selectively forming an air gap through ALD or CVD processes resulting in increased performance is desired.